Roller and breast grinding mill



May 2, 1939. c. CARRUTHERS v ROLLER AND BREA ST GRINDING MILL 5 Sheets-Sheet 1,

Filed Nov. '7, 1936 T R M /N\/EN 0 ATTORNEY y 2, 1939- I c. CARRUTHERS 2,156,618

ROLLER AND BREAST GRINDING MILL Filed Nov. 7, 1936 5 Sheets-Sheet 2 lNVENTOR M BY flak/772% ATTORNEY.

y 1939- c. CARRUTHERS 2,156,618

I ROLLER AND BREAST GRINDING MILL Filed Nov. 7, 1956 5 Sheets-Sheet 3 Fig.4.

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lNVE/VTOR M WM, BY

ATTOR NEY.

y 1939- c. CARRUTHERS ROLLER AND BREAST GRINDING MILL 5 Sheets-Sheet 4 Filed Nov. 7, 1936 l I INVENITOR @4 4 KM BY v ATTORNEY,

May 2, 1939.

C. CARRUTHERS ROLLER AND BREAST GRINDING MILL 5 Sheets-Sheet 5 Filed Nov. 7, 1936 VENTOR QM ATTORNEY Patented May 2, 193% Application November 7, 1936, Serial No. 109,653 In Great Britain January 29, 1936 6 (llairns.

The present invention relates to roller and breast grinding mills such as are used in grinding, mixing, refining or finishing paints, enamels, cellulose products, inks and the like fluids, by which are included creams or pastes and is particularly applicable to mills for treating paints and the like incorporating hard colouring matters such as oxides, ochres, siennas, umbers, Prussian blue etc., with oily spirit or synthetic media.

In the manufacture of such products there are in general three stages firstly the breaking down of the aggregates and larger particles, secondly the wetting or covering of each particle with the medium and thirdly the ultimate fine grinding of the particles so wetted, though in practice these stages proceed in some degree simultaneously.

In order to enable two stages of grinding to be effected in one pass through such a mill it has been proposed to provide it with two grinding bars having a space between, the bar most remote from the hopper being adjusted for finer grinding than that nearer the hopper and also to provide passages through which any surplus material which reaches the finer grinding bar from the coarser grinding bar, owing to the pressure per unit area exerted by the latter on the roller being less than that of the former'is automatically returned to the hopper for further treatment.

According to the main feature of the present invention such surplus material, instead of being allowed to pass back freely to the hopper, is utilised to build up considerable pressure in pockets lying between the two bars.

For this purpose I employ a combination of three or more grinding bars in which the first and last, and preferably the intermediate bars, are in contact with the roller and the pressure exerted by the bar most remote from the hopper which effects the final fine grinding is higher than in the case of the other bars.

In such case the material passes the first bar more easily than the final bar and this tends to cause an accumulation of material in the pockets between the bars, whilst the provision of a plurality of pressure pockets facilitates the thorough and progressive wetting and mixing of the materials without access of air during such process which would tend to have a deleterious effect.

This achieves two objects, in that the high pressure on the pocket immediately before the fine grinding bars assists to force the material past such bar, at an economic rate, even when such bar is pressed strongly against the roller,

and also the pressure, combined with the movement of the roller, produces a strong eddying or mixing effect on the material in the pockets, thereby greatly facilitating the wetting process.

It is however necessary to control such pressures, as otherwise they might rise to a point such that injury would be caused to the apparatus, and for this purpose relief openings are provided so that on the pressure attaining a fixed limit a portion of the material in the pocket can escape. Such openings are preferably made in the end seals as hereinafter described, and may lead to a relief valve, to the exterior of the machine, to another pocket, to the hopper or to a point in advance of the fine grinding bar. In the last case it is advisable to provide a second fine grinding bar, in advance of the former to catch any large particles which may have passed through the relief passage. The pressure behind this bar may be less than that behind the first fine grinding bar, since the greater portion of the material arriving at such second bar will have already been finely ground.

It has been proposed to provide a mill with two grinding bars in order to effect two stages of grinding in one pass, the bar more remote from the hopper being adjusted for finer grinding than that nearer to the hopper, and to provide passages for transferring back to the hopper for further treatment the surplus materials which reach the final grinding bar after passing under the earlier bar.

The present invention on the contrary aims to utilize such surplus material to build up considerable pressure in the pockets between the bars for the purposes above mentioned.

The size of the relief orifices is, however, very important, since if large orifices or passages were used, little or no pressure could be set up in the pocket, whereas I desire to produce pressures in the region of '75 lbs. per square inch or more under certain working conditions which are here- .inafter more particularly described.

The main object of the present invention is therefore the establishment and regulation of the pressures in the pockets for the purposes mentioned.

A further feature is the provision of more than two bars and preferably of four bars, thus giving three pockets of the class above described. In this case the pressure of the intermediate bar or bars is in general less than those of the end bars, and with such arrangement the first bar breaks down the larger particles, and very efiective wetting takes place in the intermediate pockets.

It is also most important that the size of the pockets should not vary as the bars are worn down in use and this result I achieve by forming the pockets under spacing bars which do not actually come into contact With the roller, whilst the grinding bars can be fed forward to compensate for wear and the pockets are therefore preserved unchanged in size.

It is generally preferred to allow the material to escape from one or both ends of the pocket through end seals for the bars. I preferto avoid long narrow relief passages as there might be undue tendency for such relief passages to choke.

It is better to use relief passages of round, D, or square or like cross section, i. e., to avoid forms which are considerably narrower in one direction than in another.

Although I prefer to have each of the bars in contact with the roller, good results may be obtained where one or more of the intermediate bars although approaching closely to the roller, is not in actual contact therewith.

Where the relief passage leads back to the hopper I prefer to use a hopper with a pressure throat since the pressure prevailing in such threat tends to increase the pressure which will be maintained in the pressure pocket, and it is possible to reach pressures in the pocket as high as 190 lbs. per square inch when the mill is running at high speeds. I also prefer to lead the relief passages through the end seals to the ends of the hopper throat so that the returning liquid interferes as little as possible with the action in the throat.

In order that the invention may be the more readily understood, reference is hereinafter made to the constructional form illustrated in the accompanying drawings, in which:

Fig. 1 is a side sectional elevation and Fig. 2 a front sectional elevation of the mill.

Fig. 3 is a side view, Fig. i a plan view and Fig. 5 a cross-sectional view (along line 5-5 of Fig. 4) of one of the end seals for the bar.

Fig. 6 is a side view and Fig. 7 a plan view of a seal for the hopper ends.

Fig. 8 is a plan view of a hydraulic pressureapplying system for the bars. Figs. 9 and 10 are views of variant forms of pressure-applying mechanisms for the bars.

Fig. 11 is a sectional plan view and Fig. 12 a side view of a modified form of release device.

The mill illustrated comprises four bars I, 2, 3, 4 preferably not exceeding 1%" in thickness separated from each other by separator bars 5 the bottoms of which are spaced from the roll 6 so as to form a pocket 1 between each pair of bars.

The bars are adapted to be so set that the pressure per unit area which the last bar exerts on the roll (the last bar preferably being thinner than the other bars for this purpose) is greater than that exerted by the other bars so that more material can enter the pockets in a given time than can normally pass under the last bar and thus the material accumulates under pressure in the pockets. This pressure is utilised to assist the material to pass below the last bar, and preferably the pockets are shaped to promote the passage of the material below the next bar. For this purpose the pockets are preferably greater in width than the thickness of the bars,

and the roofs of the pockets slope towards the next following bar.

The relief passages may be formed in one or both of the end seals la. The seals are stepped to receive bars of different lengths as described and claimed in co-pending application No. 109,655, filed November 7, 1936, and the inner face of the seal is preferably formed with arcuate grooves 8a, 8b, 80, which lead the material from the end of one pocket past the end of a bar into the next pocket, the groove 8a leading into the contracted throat 9 of the hopper. Leather or other seals I0 may be inserted in the end seals above the relief grooves to contact with the ends of the bars and bar separators and prevent the material from exuding upwardly out of the ends of the mill.

Sealing of the hopper ends is completed by the seal plates ll (Figs. 6 and '7) whose edge l2 lies against a corresponding edge I3 (Fig. 4) of the seals 1a.

By way of example in a roller and breast mill above described having four bars spaced round a roller of 15 inches diameter running at a speed not exceeding 200R. P. M. and having pockets between the bars each of 4;" width and depth but having a length parallel to the axis of rotation of the roll of approximately 19", 21" and 24 respectively, I have found a cross sectional area of the relief orifice in each end seal tapering from .05 square inch at the hopper to .03 square inch at the last pocket to work well when treating such materials as high gloss paints and enamels. The size of the relief orifice may require to be varied. in accordance with varia tions in the viscosity of the material under treatment.

So far I have found in a mill proportioned and operating as above described that the total size of the relief orifice or orifices should not generally exceed .1 square inch over the range of materials hereinabove given.

The above example refers to a case where the relief orifices lead the escaping material back into the hopper throat against pressure generated therein but smaller relief orifices may be used where these lead the escaping material directly into the atmosphere.

With such a mill I have obtained good results in grinding paints with the pressure on the first and last bars so regulated as to enable a pressure of pounds per square inch to be produced in the pockets when the roll is running at 200 R. P. Ii/L'the bars intermediate the first and last bars making relatively light contacting pressure with the roll.

I have found when treating material of the kind above referred to in a mill having pockets and pocket relief orifices and the pressure on the bars regulated as above described that greater pressures in the pocket are obtained the higher the speed at which the roll rotates but for various reasons it is not generally desirable to run the roll at much higher speeds than to 200 R. P. M. Good results have been obtained when running the roll at 1'70 R. P. M. with the pressure on the bars regulated so as to build up a pressure of '75 lbs. per square inch in the pockets but when the speed was reduced to 100 R. P. M. the pressure fell to 25 lbs. per square inch, and I think it undesirable to run the roll at speeds substantially lower than 100 R. P. M. as the pressure is not only unduly lowered but the output also becomes uneconomically small.

In these experiments the hopper throat was so-contracted in accordance with Patent Number 2,134,174 issued November 1, 1938, in the name of Henry E. Cox and John R. Torrance of the'present applicant company and as shown at ii in Fig. 1 of the accompanying drawings that the pressures produced therein in the case of the three experiments were:

Hopper throat pressure lbs. per sq. inch. Roll running at 209 R. P. M 75 Roll running at 1'76 R. P. M ii) Roll running at 100 R. P. M g

tion, with ,a single pass through of the major part of the hopper charge, was found to be of a beautifully smooth soft homogeneous nature, substantially free from voids. wherein the smallest knots or uncvcnnesses were substantially smoothed out.

The bars may be of the same or difierent thickess.

The pressure upon the respective bars may be applied in any suitable manner, such as me chanically or hydraulically, and the pressure on the bars may be dependently or independently adjustable; but it preferred to employ hydraulic pressure-applying means which give a dependent adjustment as described and claimed in my concurrent application No. 109,654, dated November 7, 1936.

Such a hydraulic system may for example comprise a common. fluid-containing chest iii and multiple pistons and cylinders associated with each bar. For example a row of five large pistons 51 can be spaced along the length of the fine-grinding bar 1, and four pistons it of the same size spaced along the first bar l, while rows of smaller pistons i9, 28 can be used to exert the smaller pressure on the intermediate bars. A common plunger Zfittactuated by the handwheel 263?:- of a screw 2% may be used to adjust the pressure simultaneously on all or" the bars.

Instead of using hydraulic pressure the multiple breast bars may be yieldingly urged as a whole towards the roll (as shown in Fig. 9) in such wise that the working pressure exerted on the film when passing between the breast bar and the roll may be predetermined by the locked setting of an adjustable spring action or actions.

In this connection a parallel micrometer adjustment of the multiple breast bars is preferred so that these can be brought into contact with the roll with little or no or the desired pressure, or, otherwise, into a desired non-contacting setting.

For this purpose it is convenient to slidingly mount the multiple breast bars 5, 2, d in a correspondingly slotted sheath or housing 2E which in turn is mounted in a breast frame so as to be capable of a radial sliding movement with respect to the roll.

Provision for regulating and maintaining the working pressure may be made by hand micrometer controls of which advantageously there may be two disposed longitudinally of the sheath or housing. Each such control may consist of a strong cylindrical compression spring 23 having its end remote from the roll bearing against an internal shoulder of a recessed boss 24 in the breast frame cap and having its other end bearing against the lower flanged end 25 of a tube 25 which passes through and projects beyond the upper end of the boss and is there externally screw threaded to take a nut 27, the tightening or slackening of which adjusts the spring to re-' act at a predetermined valueduring the passage of the material between the breast bars and the oll.

The above mentioned tube is internally screw threaded and receives a micrometer screw 28 to which a calibrated scale is related, the screw passing through the tube to bear against the breast sheath or housing.

In this way all the breast bars are controlled in working movement with respect to the roll as one unit.

The bar housing is preferably mounted independently of the hopper and as shown is pivotally mounted at 28aon the frame of the mill so that this and the hopper which is hinged at may each hinge back or rise alone for cleaning etc.

In addition to the collective setting effected by the hand-wheel operated screw 28, each breast bar 5, 2, Al, is given an independent screw adjustment in the sheath or housing. Each of such adjustments may be arranged to give a dead or yielding pressure of the corresponding breast bar against is roll. In Fig. 9 the independent adjustment is effected by associating with each bar a screw 330 which is arranged to be axially moved by an axially fixed rotatable sleeve nut Fig. 9 is a composite sectional view so that only one such nut and one such screw are shown, but a similar nut and screw is provided for each bar.

In the other variant shown in Fig. 10, the bars are adjusted by screws 3f], 35, 32, 33, which have integral hand 3m, a, 32a, 33a. Lock nuts 3th, are provided so that after adjustment the screw can be locked.

In the modified release device shown in Figs. 11 and 12, the material is not taken directly back to the hopper, but each pocket subsequent to the first is relieved by a passage 3d, 34a leading into a passage 35 which communicates with the first pocket by way of passage 36. The take-off passage 3'! may be valve controlled and a regulation of the rate of escape of material may be thereby achieved.

The preferred shape of the pressure pockets is one figured by a radial face of the preceding breast, the surface of the roll, and a concave roof inclined downwardly in the direction of rotation of the roll, but the pockets may be bounded at the sides by opposite radial faces of adjacent breasts as in. the first embodiment described.

What I claim is:

1. A multi-stage roller and breast mill for treating fluid material containing particles to be wetted by intimate therewith, comprising a grinding roll; at least three axially disposed grinding bars normally maintained in grinding relation with said roll, a hopper overlying said roll. and disposed to feed fluid material to said grinding bars, each of said bars except the first bar in the direction of rotation of the roll having a longitudinally co-extensive material receiving pocket provided at the hopper side thereof; seals abutting the ends of said bars for retaining in said pockets material undergoing treatment; at least one of said seals having restricted passages communicating with the pockets for bleeding material out of the pockets thereby to maintain a relatively high predetermined maximum pressure therein, said high pressure assisting in the forcing of the material past the grinding bars and to produce a strong eddying or mixing effect on the material in the pockets for facilitating the wetting process.

2. A multi-stage roller and breast mill for treating fluid material containing particles to be wetted by intimate mixing therewith, comprising a grinding roll; at least four grinding bars set in operative grinding relation axially of said roll, at least one bar beyond the third bar in the direction of rotation of the roll being set for finer grinding than the preceding bars and at least one intermediate bar being set in close proximity to the roll, and each of the intermediate bars having a longitudinally co-extensive material collecting pocket formed at .each side thereof; end seals abutting the ends of said bars and engaging the roll for retaining a portion of the material undergoing treatment in said pockets, one ofsaid seals having pressure relief orifices formed therein for bleeding material out of said pockets, each of said orifices being of a size such that material accumulating and retained in said pockets when the roll is rotating is maintained therein under a predetermined high pressure, said high pressure producing a strong eddying or mixing effect on the material in the pockets for facilitating the wetting process and assisting in the forcing of the material past the grinding bars.

3. A multi-stage roller and. breast mill for treating fluid material containing particles to be wetted by intimate mixing therewith, comprising a grinding roll and a plurality of grinding bars in axial operative contact with said roll, at least one bar beyond the second bar in the direction of flow of the material being set for finer grinding than the preceding bars, and each of said intermediate bars having a longitudinally co-extensive pocket formed on each side thereof; end seals abutting the ends of said bars for retaining a portion of the material undergoing treatment in said pockets under high pressure; a pressure relief conduit in one of said seals communicating with said pockets for bleeding material out of the pockets; and a valve in said relief conduit for regulating the escape of material and thereby the value of the high pressure maintained in the pockets, said high pressure assisting in the forcing of the material past the fine grinding bar and producing a strong eddying or mixing effect on the material in the pockets.

4. A multi-stage roller and breast mill for treating fluid material containing particles to be Wetted by intimate mixing therewith, comprising a material hopper; a grinding roll receiving material therefrom; a plurality of successively arranged grinding bars normally maintained in preselected axial grinding relation with said roll, each of said bars except the first bar in the direction of flow of material having a longitudinally co-extensive pocket at the hopper side thereof; end seals abutting the ends of said bars and engaging the roll for retaining material undergoing treatment in said pockets, each of said seals having restricted passages therein communicating between successive pockets, and a second restricted. passage therein establishing communication between the first, pocket in the direction of flow of material and the hopper, said passages having a sectional area such that material accumulating and retained in said pockets when the roll is rotating attains a relatively high pressure whereby to assist in the forcing of the material past the grinding bars and producing a strong eddying or mixing effect on the material in all of the pockets for facilitating the wettin process.

5. A multi-stage roller and breast mill for treating fluid material containing particles to be wetted by intimate mixing therewith, comprising a grinding roll; a plurality of successively arranged grinding bars normally maintained in preselected axial grinding relation with said roll; separator bars interposed between said grinding bars, said separator bars having their lower edges spaced from the said roll and cooperating to form longitudinally co -extensive material collecting pockets between the grinding bars, the lower edges of said separator bars being curved downwardly toward the next succeeding grinding bar in the direction of flow of material; end seals abutting the ends of said bars and engaging the roll for retaining material undergoing treatment in said curved pockets, one of said seals affording restricted passage for bleeding material out of the pockets, said passages having a sectional area such that material accumulating and retained in said pockets when the roll is rotating is maintained therein at a predetermined high pressure whereby to assist in the forcing of the material past the grinding bars and producing a strong eddying or mxing effect on the material in the pockets for facilitating the wetting process.

6. A multi-stage roller and breast mill for treating fluid material containing particles to be wetted by intimate mixing therewith, comprising a grinding roll, at least three axially disposed grinding bars arranged in succession in contact with said roll, a hopper overlying said roll and disposed to feed fluid material to said grinding bars, the last bar in the direction of rotation of the roll being set for finer grinding than the preceding bars, and the intermediate bar being pressed toward the roll at less pressure than the first bar, all of said bars except the first bar in the direction of rotation of the roll having a longitudinally co-extensive material collecting pocket provided at the hopper side thereof; and seals abutting the ends of said bars for retaining in said pockets material undergoing treatment; at least one of said seals having restricted passages communicating with the pockets for bleeding material out of the pockets thereby to maintain a relatively high predetermined maximum pressure therein, said high pressure asisting in the forcing of the material past the grinding bars and to produce a strong eddying or mixing effect on the material in the pockets for facilitating the wetting processv CHARLES CARRUTHERS. 

